Spectroscopic evidence for possible quantum spin liquid behavior in a two-dimensional Mott insulator

Abstract

Mott insulators with localized magnetic moments will exhibit a quantum spin liquid (QSL) state when the quantum fluctuations are strong enough to suppress the ordering of the spins. Such an entangled state will give rise to collective excitations, in which spin and charge information are carried separately. Our angle-resolved photoemission spectroscopy (ARPES) measurements on single-layer 1T-TaS2 show a flat band around the zone center and a gap opening of about 200 meV in the low temperature, indicating 2D Mott insulating nature in the system. This flat band is dispersionless in momentum space but shows anomalously broad width around the zone center and the spectral weight decays rapidly as momentum increases. The observation is described as a spectral continuum from electron fractionalization, corroborated by a low energy effective model.The intensity of the flat band is reduced by surface doping with magnetic adatoms and the gap is closing, a result from the interaction between spin impurities coupled with spinons and the chargons, which gives rise to a charge redistribution. Doping with nonmagnetic impurities behaves differently as the chemical potential shift dominates. These findings provide insight into the QSL states of strongly correlated electrons on 2D triangular lattices.

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Cited by in corpus (6)

• Orbital textures and evolution of correlated insulating state in monolayer 1T phase transition metal dichalcogenides
• Tunneling spectroscopy of the spinon-Kondo effect in one-dimensional Mott insulators
• Topical review: the nature of the ground state and possibility of a quantum spin liquid in 1T metal dichalcogenides
• Van der Waals devices for surface-sensitive experiments
• Emergent quantum phenomena in two-dimensional 1T-TaS2
• Strongly Enhanced Charge-Density Waves and Correlated Insulating State in Atomically Thin 1$T$-TaS${}_2$